A number of conventional methods exist for measuring fluid velocities in well formations producing gas, oil, or water.
In FIGS. 1 and 2 are shown two prior art devices for measuring fluid velocity in a well bore. In FIG. 1, the well bore 10 is shown to contain a multi-phase fluid 20 moving in the direction of arrow 30. The multi-phase fluid 20 contains, for example, a mixture of oil and gas or oil, gas and water in differing amounts. In slant bore hole 10, such multi-phase fluids moving in the direction of arrow 30 typically undergo stirring action which creates circulating cells 40 that move upwardly with the fluid 20.
In FIG. 1 is shown a conventional spinner or turbine meter 50 which spins in response to the fluid flowing through it. In slant bore hole configurations, such spinners 50 are typically oriented close or near the lower edge 60 of the bore hole 10. The region of the fluid 20 near edge 60 is typically the region in which the stirring action 40 most frequently occurs. Depending upon the composition of the multi-phase fluid and its location, a conventional spinner 50 may, at times, actually be caused to be driven in the reverse direction by the stirring action 40 thereby resulting in the possibility of an erroneous reading as to the true upward velocity rate of the fluid 20 in the direction of arrow 30. The measurements must be individually made at different locations in the bore hole.
Another conventional prior art approach is shown in FIG. 2 and is commonly called a "packer flow meter". The packer flow meter 200 comprises a packer portion 210 and a centrally disposed spinner 220 suspended from a wire-line or cable 230. In operation, the packer portion 210 is collapsed about its central section 240 while it is being lowered into the bore hole 10. When it is at its desired depth, the packer portion 210 is expanded outwardly in the direction of arrow 250 to firmly abut against the inside edges of the bore hole 10. In this configuration, the instrument is firmly "packed" into place in a fixed position. The fluid 20 is now caused to enter the central region 240 and to pass through the spinner 220; the fluid then exits upwardly into bore hole 10. As can be observed in FIG. 2, the stirring action 40 is prohibited from occurring and the device provides an overall accurate reading of the velocity of the fluid flow 20. The packer flow meter set forth in FIG. 2, however, is usable only for low velocity fluid flow and will not work for high velocity flows. In high velocity flow situations the restriction created by confining the fluid flow through channel 240 causes the packer flow meter to slide upwardly or possibly to be blown out of the bore hole due to a fluid pressure buildup. For each separate location, the packer flow meter must be deflated and re-packed to provide readings.
As the result of a patentability search conducted for the present invention, the following prior art approaches were uncovered:
______________________________________ Patent No. Inventor Issue Date ______________________________________ (U.S.) 2,158.569 L. Bowen 5-16-39 (U.S.) 2,277,898 T. A. Andrew 3-31-42 (U.S.) 2,674,877 D. Silverman, 4-13-54 et al (Aust) 262,730 Heel, et al 3-21-62 (U.S.) 3,839,914 Modisette, et al 10-8-74 (U.S.) 3,871,218 Louis 3-18-75 ______________________________________
The 1954 patent issued to Silverman, et al sets forth a well productivity measurement method that utilizes an injected identifiable liquid barrier such as an oil emulsion or an oil base gel. This identifiable fluid body is pushed upwardly in the well bore by the fluids at a rate substantially equal to the velocity of the fluids. Silverman utilizes a set of contacts of identify the interface between the fluids and the identifiable fluid body. By pulling the contacts upwardly and preserving the contact interface, the velocity of the fluids can be ascertained. However, the Silverman, et al approach is not adapted for slanted bore holes and is especially not adapted for multi-phase fluids exhibiting stirring action. The mere presence of stirring action would cause the identifiable fluid body to substantially intermix with the multi-phase fluids causing Silvermans's approach to be inoperative.
In the Modisette, et al approach, fluid must be caused to flow through a separate conduit at the surface of the bore hole. Such an approach is not suitable for measuring the velocities of the different formations.
The 1942 Andrew approach utilizes a differential pressure measurement by sensing pressure above and below its probe. The probe, however, is designed to remain stationary in the bore hole as the fluids flow upwardly therefrom. The probe will record the differential pressure at that position in the bore hole. The probe is then moved to a new position and the differential pressure is recorded at the new position. The mechanism for recording the differential pressure is located in the interior of the probe. The 1939 patent issued to Bowman relates to a formation tester to ascertain whether or not perforations in the bore hole are plugged. The 1975 patent issued to Louis relates to an apparatus which performs a number of tests ascertaining the permeability characteristics of a coarse or fissured medium. Specifically, Louis uses a conventional spinner flow meter to measure velocity flow. The 1962 Australian patent issued to Heel, et al also relates to an apparatus for testing petroleum formations. Again, Heel, et al utilizes a spinner element 46 for sensing flow rates.